If you're growing a weigela (Weigela spp.) or you're thinking of planting one, you probably know that it's an especially easy-to-grow shrub. A tough plant that has masses of colorful flowers in late spring or early summer, a weigela is cold-tolerant and grows in U.S. Department of Agriculture plant hardiness zones 4 through 9, depending on the variety. Whatever type of weigela you grow, it's a good idea to give it a bit of extra care as winter approaches and at winters end to help keep it flourishing.
Although a weigela is a deciduous plant that drops its leaves in fall, its roots continue functioning for a while and don't become dormant as quickly as the top growth. Because of this, it's important to support good root growth during fall, especially if your weigela is newly planted. Continue watering the shrub during fall, giving it extra water whenever the top 1 to 2 inches of its soil feel dry to the touch. Moist soil also tends to stay warm longer than dry soil, so watering through fall helps keep the roots warm.
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Adding a 6- or 8-inch layer of organic mulch, such as straw or shredded bark, in fall helps conserve soil moisture and keeps roots growing as long as possible. In cold-winter areas, mulch also protects the plant from freeze-thaw cycles that cause the ground to expand and contract. These cycles can heave roots out of the ground and damage them.
Winter Sun Damage
Because a weigela has no leaves in winter, its stems are susceptible to a problem called sun scald, which happens when sun heats up the bark on bright but cold days, stimulating activity in the stem that can be followed by tissue damage when the sun goes down and the stem is chilled. This is especially likely in a young or recently transplanted shrub, or in one planted where its south-facing side is unprotected. If sun scald develops, you'll see dried or cracked bark, or areas on a stem that are sunken or shriveled.
You can help prevent sun scald by wrapping the larger stems on a weigela with a commercial tree wrap or a light-colored plastic tree guard. If your weigela is bushy and has only thin stems that aren't easily wrapped, provide some shade on the south-facing side by stapling a sheet of burlap to two or three stakes driven into the ground near the south-facing side of the shrub.
You can also protect a weigela from sun scald by painting its stems with white or light-colored paint that reflects the sun, but only use latex paint, not an oil-based paint.
At Winter's End
Although weigela is a hardy plant, it's prone to winter dieback, especially in areas with harsh winters. Because of this, it's a good idea to examine the plant at the end of winter and prune off any dead stems.
Double-check stems that look dead by scratching the bark with a fingernail. If tissue under the bark is greenish white, the stem is healthy, but dry tissue indicates the stem has died back.
Remove dead stems by cutting into healthy tissue behind the damaged part, using sharp shears or a pruning knife that you wipe with rubbing alcohol between each cut to prevent spreading disease.
You can also remove any broken or damaged branches at the end of winter, but a weigela has its heaviest flowering in spring on the previous season's growth, so it's best you don't prune heavily in winter to preserve flower buds. If your shrub is older and overgrown, you can stimulate its growth by pruning off a few large branches at the end of winter. Cut these off near the shrub's base to let light into its interior so new shoots can form.